1. Field of the Invention
The present invention relates to a white balance regulating device and a method thereof, particularly, to a white balance regulating device which regulates a cut-off point and a saturation point of a digital display, such as a liquid crystal display (LCD) and a plasma display panel (PDP), etc., and a method thereof. The present application is based on Korean Patent Application No. 2002-27934, which is incorporated herein by reference.
2. Description of the Related Art
In order to display an analog image signal input from an external apparatus on a digital display such as an LCD and a PDP, etc., the analog image signal has to be converted into a digital image signal. Therefore, it is important to match black level and white level of the analog image signal input from the external apparatus with a digital value of the digital image signal.
Therefore, in order to fully reproduce a color of an image, the digital display used in a TV or a monitor, etc. sets a cut-off point for regulating a balance of a red, green and blue (RGB) color signal in the black level which emits a dim light, and adjusts a saturation point for regulating the balance of the RGB color signal in the white level which emits a strong light.
FIG. 1 is a block diagram showing a conventional white balance regulating device.
Referring to FIG. 1, a white balance regulating device comprises a level regulating portion 100, an A/D converter 110, a data detecting portion 120, a controlling portion 130 and a displaying portion 140. The level regulating portion 100 variably regulates a level of a variable register to set the cut-off point and the saturation point of the RGB color signal input from the external apparatus. The A/D converter 110 converts an analog RGB color signal output from the level regulating portion 100 into an 8-bit digital signal.
The data detecting portion 120 detects all the data of the 8-bit digital RGB color signal. The controlling portion 130 compares all the data of the 8-bit digital RGB color signal detected from the data detecting portion 120 with predetermined standard data, and then controls the level regulating portion 100 so as to regulate the variable register according to the compared result. The displaying portion 140 receives a signal output from the data detecting portion 120, and drives a liquid crystal to display on a screen.
For example, the controlling portion 130 initializes the cut-off point to a desired data 0x00 so as to regulate the cut-off point of the RGB color signal input from the external apparatus. Further, after initializing the cut-off point, the controlling portion 130 sets the variable register of the level regulating portion 100 to a desired value to perform a regulation of the cut-off point. The controlling portion 130 compares the 8-bit data of the RGB color signal detected by the data detecting portion 120 with desired data.
If the data detected by the data detecting portion 120 is equal to the desired data, the controlling portion 130 controls the level regulating portion 100 to gradually increase the level of the variable register until obtaining an optimal cut-off point. The level regulating portion 100 regulates the level of the variable register according to a control signal of the controlling portion 130. If the 8-bit data of the RGB color signal read through the regulated variable register of the level regulating portion 100 is larger than the desired data, the corresponding level of the variable register is set as the cut-off point.
In order to set a saturation point, the saturation point is initialized to a desired data 0xFF. After setting the variable register to a desired value, the controlling portion 130 compares the RGB signal read through the data detecting portion 120 with the initialized data.
If the data detected by the data detecting portion 120 equals the desired data, the controlling portion 130 controls the level regulating portion 100 to gradually reduce the level of the variable register until obtaining an optimal saturation point. The level regulating portion 100 regulates the level of the variable register according to a control signal of the controlling portion 130. If each data corresponding to the RGB color signal read through the regulated variable register of the level regulating portion 100 is smaller than the desired data, the corresponding level of the variable register is set as the saturation point.
However, in the conventional white balance regulating device, since the data detecting portion 120 has to read all the 8-bit digital data corresponding to each digital RGB color signal output through the A/D converter 110, there is a problem that a circuit construction of the white balance regulating device becomes complicated.
In addition, if the cut-off point and the saturation point are not optimized, when the input analog image signal is converted into the digital image signal, a signal distortion phenomenon occurs, whereby an image signal corresponding to a dark portion is cut off, and thus is not displayed, or an image signal corresponding to a bright portion is saturated, and thus is not displayed.